So, with MacOs and Windows come a lot of system fonts. – Is it legal to convert the system fonts into .woff2 etc and embed them (self-host) on a web site?
I'm of course aware that I could display them as regular system fonts, but if I, for example, would want to display the MacOs system font San Fransisco to all users, including Windows users it would be better to self-host them.
I believe there is no "one size fits all" answer for this. Make sure to check the license of each font you'd like to embed.
For the Apple SF font, the answer seems to be a clear no (see here).